Came up with this thread after yet another viewing of The Godfather.Classic scenes in the movie include the double shooting at the restauraunt,the killing of luca brasi(sleeps with the fishes) and the gunning down of Sonny at the tollbooth.

Apart from those Godfather ones..how about

Alien-John Hurt chest bursting scene
Psycho-shower scene
Scanners-exploding head
Carrie-crucified mother
The Deer Hunter-russian roulette
The Wizard Of Oz-"I'm melting!"